U.S. patent application number 16/061224 was filed with the patent office on 2018-12-13 for additive for non-aqueous electrolyte.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS LLC. The applicant listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Shawn DENG.
Application Number | 20180358656 16/061224 |
Document ID | / |
Family ID | 59310593 |
Filed Date | 2018-12-13 |
United States Patent
Application |
20180358656 |
Kind Code |
A1 |
DENG; Shawn |
December 13, 2018 |
ADDITIVE FOR NON-AQUEOUS ELECTROLYTE
Abstract
A non-aqueous electrolyte includes a solvent, a lithium salt,
and an additive selected from: formulas, and combinations thereof.
R.sub.1, R.sub.2, and R.sub.3 are independently selected from: a
linear or branched alkyl having a formula C.sub.nH.sub.2n+1 (n
ranges from 1 to 20); a linear or branched alkoxyl having a formula
C.sub.2H.sub.2n+1O (n ranges from 1 to 20); a linear or branched
either having a formula C.sub.nH.sub.2n+1OC.sub.mH.sub.2m (n and m
each range from 1 to 10); phenyl; a mono-substituted phenyl with
one linear or branched alkyl having a formula C.sub.nH.sub.2n+1 (n
ranges from 1 to 20); a di-substituted phenyl with two linear or
branched alkyls, each alkyl having a formula C.sub.nH.sub.2n+1 (n
ranges from 1 to 20); a tri-substituted phenyl with three linear or
branched alkyls, each alkyl having a formula C.sub.nH.sub.2n+1 (n
ranges from 1 to 20); and combinations thereof. X, Y, and Z are
halides. ##STR00001##
Inventors: |
DENG; Shawn; (Shanghai,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC |
Detroit |
MI |
US |
|
|
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS
LLC
Detroit
MI
|
Family ID: |
59310593 |
Appl. No.: |
16/061224 |
Filed: |
January 15, 2016 |
PCT Filed: |
January 15, 2016 |
PCT NO: |
PCT/CN2016/071015 |
371 Date: |
June 11, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 10/052 20130101;
H01M 10/0525 20130101; H01M 10/0567 20130101; Y02E 60/10 20130101;
H01M 10/0569 20130101; H01M 2300/0042 20130101; H01M 10/0568
20130101 |
International
Class: |
H01M 10/0567 20060101
H01M010/0567; H01M 10/0569 20060101 H01M010/0569; H01M 10/0568
20060101 H01M010/0568; H01M 10/0525 20060101 H01M010/0525 |
Claims
1. A non-aqueous electrolyte, comprising: a solvent; a lithium
salt; and an additive selected from the group consisting of
##STR00005## and combinations thereof; wherein: R.sub.1, R.sub.2,
and R.sub.3 are independently selected from the group consisting of
a linear or branched alkyl having a formula C.sub.nH.sub.2n+1,
wherein n ranges from 1 to 20; a linear or branched alkoxyl having
a formula C.sub.nH.sub.2n+1O, wherein n ranges from 1 to 20; a
linear or branched ether having a formula
C.sub.nH.sub.2n+1OC.sub.mH.sub.2m, wherein n ranges from 1 to 10
and m ranges from 1 to 10; phenyl; a mono-substituted phenyl with
one linear or branched alkyl having a formula C.sub.nH.sub.2n+1,
wherein n ranges from 1 to 20; a di-substituted phenyl with two
linear or branched alkyls, each alkyl having a formula
C.sub.nH.sub.2n+1, wherein n ranges from 1 to 20; a tri-substituted
phenyl with three linear or branched alkyls, each alkyl having a
formula C.sub.nH.sub.2n+1, wherein n ranges from 1 to 20; and
combinations thereof; and X, Y, and Z are each a halide.
2. The non-aqueous electrolyte as defined in claim 1 wherein the
halide is selected from the group consisting of fluorine, chlorine,
bromine, and iodine.
3. The non-aqueous electrolyte as defined in claim 1, wherein the
additive is ##STR00006## R.sub.1, R.sub.2, and R.sub.3 are each
C.sub.2H.sub.5, and X is chlorine.
4. The non-aqueous electrolyte as defined in claim 3 wherein: the
solvent is a mixture of propylene carbonate, ethylene carbonate,
dimethyl carbonate, diethyl carbonate, and methyl butyrate; and the
lithium salt is LiPF.sub.6.
5. The non-aqueous electrolyte as defined in claim 1 wherein the
additive is present in an amount ranging from about 0.01 wt. % to
about 10 wt. % of a total weight of the non-aqueous
electrolyte.
6. The non-aqueous electrolyte as defined in claim 1 wherein: the
solvent is selected from the group consisting of ethylene
carbonate, propylene carbonate, butylene carbonate, fluoroethylene
carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl
carbonate, methyl butyrate, methyl formate, methyl acetate, methyl
propionate, .gamma.-butyrolactone, .gamma.-valerolactone,
1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane,
tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane,
tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl
ether, and mixtures thereof; and the lithium salt is selected from
the group consisting of lithium bis(trifluoromethylsulfonyl)imide
(LiN(CF.sub.3SO.sub.2).sub.2 or LiTFSI), LiNO.sub.3, LiPF.sub.6,
LiBF.sub.4, LiI, LiBr, LiSCN, LiClO.sub.4, LiAlCl.sub.4,
LiB(C.sub.2O.sub.4).sub.2 (LiBOB), LiB(C.sub.6H.sub.5).sub.4,
LiBF.sub.2(C.sub.2O.sub.4) (LiODFB), LiN(SO.sub.2F).sub.2 (LiFSI),
LiPF.sub.3(C.sub.2F.sub.5).sub.3 (LiFAP),
LiPF.sub.4(CF.sub.3).sub.2, LiPF.sub.4(C.sub.2O.sub.4) (LiFOP),
LiPF.sub.3(CF.sub.3).sub.3, LiSO.sub.3CF.sub.3, LiAsF.sub.6, and
combinations thereof.
7. The non-aqueous electrolyte as defined in claim 1, further
comprising another additive selected from the group consisting of
vinylene carbonate, vinyl ethylene carbonate, fluoro ethylene
carbonate, 1,3-propane sultone, methylene methane disulfonate), and
combinations thereof.
8. A lithium ion battery, comprising: a positive electrode; a
negative electrode including lithium titanate; a separator
positioned between the positive electrode and the negative
electrode; and a non-aqueous electrolyte, including: a solvent; a
lithium salt; and an additive selected from the group consisting of
##STR00007## and combinations thereof; wherein: R.sub.1, R.sub.2,
and R.sub.3 are independently selected from the group consisting of
a linear or branched alkyl having a formula C.sub.nH.sub.2n+1,
wherein n ranges from 1 to 20; a linear or branched alkoxyl having
a formula C.sub.nH.sub.2n+1O, wherein n ranges from 1 to 20; a
linear or branched ether having a formula
C.sub.nH.sub.2n+1OC.sub.mH.sub.2m, wherein n ranges from 1 to 10
and m ranges from 1 to 10; phenyl; a mono-substituted phenyl with
one linear or branched alkyl having a formula C.sub.nH.sub.2n+1,
wherein n ranges from 1 to 20; a di-substituted phenyl with two
linear or branched alkyls, each alkyl having a formula
C.sub.nH.sub.2n+1, wherein n ranges from 1 to 20; a tri-substituted
phenyl with three linear or branched alkyls, each alkyl having a
formula C.sub.nH.sub.2n+1, wherein n ranges from 1 to 20; and
combinations thereof; and X, Y, and Z are each selected from the
group consisting of fluorine, chlorine, bromine, and iodine.
9. The lithium ion battery as defined in claim 8 wherein the
non-aqueous electrolyte further comprises another additive selected
from the group consisting of vinylene carbonate, vinyl ethylene
carbonate, fluoro ethylene carbonate, 1,3-propane sultone,
methylene methane disulfonate), and combinations thereof.
10. The lithium ion battery as defined in claim 8, wherein: the
additive is ##STR00008## R.sub.1, R.sub.2, and R.sub.3 are each
C.sub.2H.sub.5, and X is chlorine; the solvent is a mixture of
propylene carbonate, ethylene carbonate, dimethyl carbonate,
diethyl carbonate, and methyl butyrate; and the lithium salt is
LiPF.sub.6.
11. The lithium ion battery as defined in claim 8 wherein the
additive is present in an amount ranging from about 0.01 wt. % to
about 10 wt. % of a total weight of the non-aqueous
electrolyte.
12. The lithium ion battery as defined in claim 11 wherein: the
solvent is selected from the group consisting of ethylene
carbonate, propylene carbonate, butylene carbonate, fluoroethylene
carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl
carbonate, methyl butyrate, methyl formate, methyl acetate, methyl
propionate, .gamma.-butyrolactone, .gamma.-valerolactone,
1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane,
tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane,
tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl
ether, and mixtures thereof; and the lithium salt is selected from
the group consisting of lithium bis(trifluoromethylsulfonyl)imide
(LiN(CF.sub.3SO.sub.2).sub.2 or LiTFSI), LiNO.sub.3, LiPF.sub.6,
LiBF.sub.4, LiI, LiBr, LiSCN, LiClO.sub.4, LiAlCl.sub.4,
LiB(C.sub.2O.sub.4).sub.2 (LiBOB), LiB(C.sub.6H.sub.5).sub.4,
LiBF.sub.2(C.sub.2O.sub.4) (LiODFB), LiN(SO.sub.2F).sub.2 (LiFSI),
LiPF.sub.3(C.sub.2F.sub.5).sub.3 (LiFAP),
LiPF.sub.4(CF.sub.3).sub.2, LiPF.sub.4(C.sub.2O.sub.4) (LiFOP),
LiPF.sub.3(CF.sub.3).sub.3, LiSO.sub.3CF.sub.3, LiAsF.sub.6, and
combinations thereof.
13. A method, comprising: incorporating an additive into a
non-aqueous electrolyte including a solvent and a lithium salt, the
additive being selected from the group consisting of ##STR00009##
and combinations thereof; wherein: R.sub.1, R.sub.2, and R.sub.3
are independently selected from the group consisting of a linear or
branched alkyl having a formula C.sub.nH.sub.2n+1, wherein n ranges
from 1 to 20; a linear or branched alkoxyl having a formula
C.sub.nH.sub.2n+1O, wherein n ranges from 1 to 20; a linear or
branched ether having a formula C.sub.nH.sub.2n+1OC.sub.mH.sub.2m,
wherein n ranges from 1 to 10 and m ranges from 1 to 10; phenyl; a
mono-substituted phenyl with one linear or branched alkyl having a
formula C.sub.nH.sub.2n+1, wherein n ranges from 1 to 20; a
di-substituted phenyl with two linear or branched alkyls, each
alkyl having a formula C.sub.nH.sub.2n+1, wherein n ranges from 1
to 20; a tri-substituted phenyl with three linear or branched
alkyls, each alkyl having a formula C.sub.nH.sub.2n+1, wherein n
ranges from 1 to 20; and combinations thereof; and X, Y, and Z are
each a halide.
14. The method as defined in claim 13, further comprising reducing
gas production in, and improving a calendar life of a lithium ion
battery including a lithium titanate negative electrode by:
incorporating the non-aqueous electrolyte into the lithium ion
battery; and cycling the lithium ion battery.
15. The method as defined in claim 13 wherein: the additive is
present in an amount ranging from about 0.01 wt. % to about 10 wt.
% of a total weight of the non-aqueous electrolyte; X, Y, and Z are
each selected from the group consisting of fluorine, chlorine,
bromine, and iodine; the solvent is selected from the group
consisting of ethylene carbonate, propylene carbonate, butylene
carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl
carbonate, ethylmethyl carbonate, methyl butyrate, methyl formate,
methyl acetate, methyl propionate, .gamma.-butyrolactone,
.gamma.-valerolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane,
ethoxymethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran,
1,3-dioxolane, tetraethylene glycol dimethyl ether, polyethylene
glycol dimethyl ether, and mixtures thereof; and the lithium salt
is selected from the group consisting of lithium
bis(trifluoromethylsulfonyl)imide (LiN(CF.sub.3SO.sub.2).sub.2 or
LiTFSI), LiNO.sub.3, LiPF.sub.6, LiBF.sub.4, LiI, LiBr, LiSCN,
LiClO.sub.4, LiAlCl.sub.4, LiB(C.sub.2O.sub.4).sub.2 (LiBOB),
LiB(C.sub.6H.sub.5).sub.4, LiBF.sub.2(C.sub.2O.sub.4) (LiODFB),
LiN(SO.sub.2F).sub.2 (LiFSI), LiPF.sub.3(C.sub.2F.sub.5).sub.3
(LiFAP), LiPF.sub.4(CF.sub.3).sub.2, LiPF.sub.4(C.sub.2O.sub.4)
(LiFOP), LiPF.sub.3(CF.sub.3).sub.3, LiSO.sub.3CF.sub.3,
LiAsF.sub.6, and combinations thereof.
Description
BACKGROUND
[0001] Secondary, or rechargeable, lithium ion batteries are often
used in many stationary and portable devices, such as those
encountered in the consumer electronic, automobile, and aerospace
industries. The lithium ion class of batteries has gained
popularity for various reasons, including a relatively high energy
density, a general nonappearance of any memory effect when compared
with other kinds of rechargeable batteries, a relatively low
internal resistance, a low self-discharge rate when not in use, and
an ability to be formed into a wide variety of shapes (e.g.,
prismatic) and sizes so as to efficiently fill available space in
electric vehicles, cellular phones, and other electronic devices.
In addition, the ability of lithium ion batteries to undergo
repeated power cycling over their useful lifetimes makes them an
attractive and dependable power source.
SUMMARY
[0002] A non-aqueous electrolyte includes a solvent, a lithium
salt, and an additive. The additive is selected from the group
consisting of:
##STR00002##
and combinations thereof. R.sub.1, R.sub.2, and R.sub.3 are
independently selected from the group consisting of: a linear or
branched alkyl having a formula C.sub.nH.sub.2n+1 (n ranges from 1
to 20); a linear or branched alkoxyl having a formula
C.sub.nH.sub.2n+1O (n ranges from 1 to 20); a linear or branched
ether having a formula C.sub.nH.sub.2n+1OC.sub.mH.sub.2m (n and m
each range from 1 to 10); phenyl; a mono-substituted phenyl with
one linear or branched alkyl having a formula C.sub.nH.sub.2n+1 (n
ranges from 1 to 20); a di-substituted phenyl with two linear or
branched alkyls, each alkyl having a formula C.sub.nH.sub.2n+1 (n
ranges from 1 to 20); a tri-substituted phenyl with three linear or
branched alkyls, each alkyl having a formula C.sub.nH.sub.2n+1 (n
ranges from 1 to 20); and combinations thereof. X, Y, and Z are
each a halide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Features of examples of the present disclosure will become
apparent by reference to the following detailed description and
drawings, in which like reference numerals correspond to similar,
though perhaps not identical, components. For the sake of brevity,
reference numerals or features having a previously described
function may or may not be described in connection with other
drawings in which they appear.
[0004] FIG. 1 is a schematic flow diagram illustrating interaction
between an additive in a non-aqueous electrolyte and a negative
electrode active material in order to reduce gas production;
and
[0005] FIG. 2 schematically illustrates an example of a lithium ion
battery during a discharging state.
DETAILED DESCRIPTION
[0006] Many different materials may be used to create the positive
electrodes, the negative electrodes, and the electrolyte in a
lithium ion battery. The positive electrode may include an
electroactive material that can be intercalated with lithium ions,
such as lithium-transition metal oxides or mixed oxides of the
spinel type, for example LiCoO.sub.2, LiMn.sub.2O.sub.4,
LiNiO.sub.2, LiNi.sub.(1-x-y)Co.sub.xM.sub.yO.sub.2 (where
0<x<1, y<1, and M may be Al, Mn, or the like), or lithium
iron phosphates. The electrolyte typically contains one or more
lithium salts, which may be dissolved and ionized in a non-aqueous
solvent. The negative electrode may include a lithium insertion
material or an alloy host material. Example electroactive materials
for forming the negative electrode include lithium-graphite
intercalation compounds, lithium-silicon intercalation compounds,
lithium alloys and lithium titanate (Li.sub.4+xTi.sub.5O.sub.12,
where 0.ltoreq.x.ltoreq.3, such as Li.sub.4Ti.sub.5O.sub.12 (LTO),
which may be a nano-structured LTO. Contact of the negative and
positive electrode materials with the electrolyte can create an
electrical potential between the electrodes. When electron current
is generated in an external circuit between the electrodes, the
potential is sustained by electrochemical reactions within the
cells of the battery.
[0007] LTO is a particularly desirable negative electrode material.
Many Li-ion batteries can suffer from capacity fade attributable to
many factors, including the formation of a passive film known as
solid electrolyte interphase (SEI) layer over the surface of the
negative electrode (anode), which is often generated by reaction
products of the negative electrode material, electrolyte reduction,
and/or lithium ion reduction. The SEI layer formation plays a
significant role in determining electrode behavior and properties
including cycle life, irreversible capacity loss, high current
efficiency, and high rate capabilities, particularly advantageous
for power battery and start-stop battery use. LTO has a high cut
voltage (e.g., cut-off potentials relative to a lithium metal
reference potential) that desirably minimizes or avoids SEI
formation, and is a zero-strain material having minimal volumetric
change during lithium insertion and deinsertion, which enables long
term cycling stability, high current efficiency, and high rate
capabilities. Such long term cycling stability, high current
efficiency, and high rate capabilities are particularly
advantageous for power battery and start-stop battery use.
[0008] LTO is a promising negative electrode material for high
power lithium ion batteries, providing extremely long life and
exceptional tolerance to overcharge and thermal abuse. However,
when used with certain positive electrode materials and
electrolytes, LTO may potentially have certain disadvantages. For
example, it has been observed that Li.sub.4+xTi.sub.5O.sub.12 can
generate significant quantities of gas, which mainly consists of
hydrogen, within a battery cell especially at elevated temperature
conditions under charging state. Such gas formation can make it an
undesirable choice for commercial use.
[0009] Examples of the non-aqueous electrolyte disclosed herein
reduce gassing and improve the calendar life of the lithium ion
battery (which includes an LTO negative electrode) in which the
non-aqueous electrolyte is utilized. The electrolyte includes an
additive (also referred to herein as the subject additive) that is
capable of reacting with hydroxyl groups on the surface of the
negative electrode active material. The reaction between the
additive and the surface hydroxyl groups attaches the additive to
the negative electrode active material. The attachment of the
additive to the negative electrode active material reduces or
prevents the reduction of the surface hydroxyl groups, thus
reducing or preventing the release of hydrogen gas resulting from
the reduction. In the meantime, the additive reduces or prevents
the chemical decomposition of the electrolyte solvents that
re-generates hydroxyl groups, which leads to improved battery
performance and calendar life.
[0010] The non-aqueous electrolyte includes a solvent, a lithium
salt, and the additive.
[0011] The solvent is a non-aqueous, organic solvent. Examples of
the solvent include cyclic carbonates (ethylene carbonate (EC),
propylene carbonate (PC), butylene carbonate, fluoroethylene
carbonate), linear carbonates (dimethyl carbonate, diethyl
carbonate, ethylmethyl carbonate (EMC)), aliphatic carboxylic
esters (methyl butyrate, methyl formate, methyl acetate, methyl
propionate), .gamma.-lactones (.gamma.-butyrolactone,
.gamma.-valerolactone), chain structure ethers (1,2-dimethoxyethane
(DME), 1,2-diethoxyethane, ethoxymethoxyethane), cyclic ethers
(tetrahydrofuran, 2-methyltetrahydrofuran), 1,3-dioxolane (DOL or
DIOX), tetraethylene glycol dimethyl ether (TEGDME), polyethylene
glycol dimethyl ether (PEGDME), and mixtures thereof. An example of
a suitable solvent mixture includes propylene carbonate, ethylene
carbonate, dimethyl carbonate, diethyl carbonate, and methyl
butyrate (e.g., 15:5:5:5:70 v/v). Another example of a suitable
solvent mixture is propylene carbonate, ethyl methyl carbonate, and
methyl butyrate (e.g., 1:3:1, v/v).
[0012] Any suitable lithium salt may be dissolved in the
non-aqueous, organic solvent to form the non-aqueous electrolyte.
Examples of the lithium salts include LiClO.sub.4, LiAlCl.sub.4,
LiI, LiBr, LiSCN, LiBF.sub.4, LiB(C.sub.6H.sub.5).sub.4,
LiSO.sub.3CF.sub.3, lithium bis(trifluoromethylsulfonyl)imide
(LiN(CF.sub.3SO.sub.2).sub.2 or LiTFSI), LiN(FSO.sub.2).sub.2
(LiFSI), LiAsF.sub.6, LiPF.sub.6, LiB(C.sub.2O.sub.4).sub.2
(LiBOB), LiBF.sub.2(C.sub.2O.sub.4) (LiODFB),
LiPF.sub.3(C.sub.2F.sub.5).sub.3 (LiFAP),
LiPF.sub.4(C.sub.2O.sub.4) (LiFOP), LiPF.sub.4(CF.sub.3).sub.2,
LiPF.sub.3(CF.sub.3).sub.3, LiNO.sub.3, and combinations thereof.
In an example, the concentration of the lithium salt in the
non-aqueous electrolyte is about 1 M. In an example, the
concentration of the lithium salt in the non-aqueous electrolyte
ranges from about 0.5 M to about 1.5 M.
[0013] The non-aqueous electrolyte also includes the additive. This
additive may be a silicon-based additive or a carbonyl-based
additive (see representative structures below), which includes
group(s) that can react with surface hydroxyl group(s) of the
active material present in the negative electrode of the lithium
ion battery incorporating the non-aqueous electrolyte. Examples of
the additive include:
##STR00003##
and combinations thereof. In each of these structures, R.sub.1,
R.sub.2, and R.sub.3 are independently selected from the group
consisting of a linear or branched alkyl having the formula
C.sub.nH.sub.2n+1, wherein n ranges from 1 to 20; a linear or
branched alkoxyl having the formula C.sub.nH.sub.2n+1O, wherein n
ranges from 1 to 20; a linear or branched ether having the formula
C.sub.nH.sub.2n+1OC.sub.mH.sub.2m, wherein n ranges from 1 to 10
and m ranges from 1 to 10; phenyl; a mono-substituted phenyl with
one linear or branched alkyl having the formula C.sub.nH.sub.2n+1,
wherein n ranges from 1 to 20; a di-substituted phenyl with two
linear or branched alkyls, each alkyl having the formula
C.sub.nH.sub.2n+1, wherein n ranges from 1 to 20; a tri-substituted
phenyl with three linear or branched alkyls, each alkyl having the
formula C.sub.nH.sub.2n+1, wherein n ranges from 1 to 20; and
combinations thereof. Also, in some of these structures, X, Y,
and/or Z are/is a halide (e.g., fluorine (F), chlorine (Cl),
bromine (Br), or iodine (I)).
[0014] One specific example of the additive has the structure
##STR00004##
where R.sub.1, R.sub.2, and R.sub.3 are each C.sub.2H.sub.5, and X
is chlorine. This additive is known as triethyl chlorosilane or
chlorotriethylsilane or TECS.
[0015] The additive is included in the non-aqueous electrolyte in
an amount ranging from about 0.01 wt. % to about 10 wt. % of a
total weight of the electrolyte. As an example, about 2 wt. % of
the additive is included in the non-aqueous electrolyte.
[0016] As mentioned above, the additive includes group(s) that can
react with surface hydroxyl group(s) of the active material present
in the negative electrode of the lithium ion battery incorporating
the non-aqueous electrolyte. In some examples, the halide reacts
with the surface hydroxyl group(s) of the active material, and in
other examples, the anhydride reacts with the surface hydroxyl
group(s) of the active material.
[0017] A schematic illustration of the interaction between the
additive and the negative electrode active material is depicted in
FIG. 1. As illustrated, the negative electrode active material 12
is lithium titanate (Li.sub.4+xTi.sub.5O.sub.12, where
0.ltoreq.x.ltoreq.3) having some surface hydroxyl (OH) groups. At
reference character A in FIG. 1, the negative electrode active
material 12 is exposed to the non-aqueous electrolyte 10, which
includes the additive 14. In the example shown in FIG. 1, the
additive 14 is triethyl chlorosilane. Without being bound to any
theory, it is believed that the chlorine atom of the additive 14
(or other halide or anhydride group of another additive 14) reacts
with the OH group of the active material 12, such that the chlorine
group leaves (e.g., in the form of HCl) and the remainder of the
additive 14 bonds to the oxygen atom on the surface of the active
material 12.
[0018] Reference character B in FIG. 1 illustrates the adsorption
of the solvent of the non-aqueous electrolyte 10 on the surface of
the active material 12. The solvent is absorbed onto the LTO
surface due to interaction similar to hydrogen bonding.
[0019] As illustrated in FIG. 1 after reference character B, the
surface oxygen and hydroxyl groups are bonded to the solvent and
additive 14, respectively. As such, the hydroxyl groups are not
free to undergo reduction, which would otherwise release hydrogen
gas and form oxygen atoms on the surface of the active material 12
(reference character C). Additionally, the electrolyte solvents are
not free to undergo chemical decomposition, which would otherwise
regenerate hydroxyl groups on the surface of the active material 12
(reference character D). The regeneration of hydroxyl groups can
lead to a catalytic cycle. Since oxygen atoms and hydroxyl groups
are not regenerated at the surface of the active material,
subsequent cycles (reference character E) of gas generation and
electrolyte solvent decomposition are avoided. In other words, the
additive disclosed herein breaks the catalytic cycle that results
in the formation of hydrogen gas and decomposition of the
electrolyte.
[0020] A specific example of the non-aqueous electrolyte including
the additive 14 shown in FIG. 1, namely triethyl chlorosilane, also
includes a mixture of propylene carbonate, ethylene carbonate,
dimethyl carbonate, diethyl carbonate, and methyl butyrate as the
solvent and LiPF.sub.6 as the lithium salt.
[0021] The non-aqueous electrolyte may also include a number of
other additives, such as solvents and/or salts that are minor
components of the electrolyte. Examples of these other additives
include vinylene carbonate (VC), vinyl ethylene carbonate (VEC),
fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), methylene
methane disulfonate, etc. While some examples have been given
herein, it is to be understood that many other additives could be
used as long as they don't react with the subject additive. When
included, these other additives may make up from about 0.01 wt. %
to about 15 wt. % of the total weight of the non-aqueous
electrolyte.
[0022] As mentioned above, the non-aqueous electrolyte 10 may be
used in a lithium ion battery, which includes a negative electrode
with an active material 12 that has hydroxyl groups on the surface
thereof. An example of the lithium ion battery 20 is shown in FIG.
2.
[0023] As mentioned above, the negative electrode 16 includes an
active material 12 that has hydroxyl groups on the surface thereof.
The active material 12 may be lithium titanate
(Li.sub.4+xTi.sub.5O.sub.12), where x ranges from 0 to 3 depending
on the state of charge (SOC). The lithium titanate may be present
in an amount ranging from about 85 weight percent (wt. %) to about
95 wt. % based on a total weight of the negative electrode 16. The
primary particle size of the lithium titanate is less than 2 .mu.m.
The particle size distribution of the lithium titanate has D50 of
less than 10 .mu.m and D 95 of less than 30 .mu.m. In other words,
50% of the lithium titanate particles have a size smaller than 10
.mu.m, and 95% of the lithium titanate particles have a size
smaller than 30 .mu.m.
[0024] The negative electrode 16 may also include a binder present
in an amount ranging from about 1 wt. % to about 8 wt. % based on
the total weight of the negative electrode 16. In an example, the
binder is present in an amount ranging from 2 wt. % to about 8 wt.
% based on the total weight of the negative electrode 12. The
binder may be polyvinylidene fluoride (PVDF),
polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), ethylene
propylene diene monomer (EPDM) rubber, carboxymethyl cellulose
(CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA),
cross-linked polyacrylic acid-polyethylenimine, lithium
polyacrylate (LiPAA), cross-linked lithiated polyacrylate,
polyimide, carboxymethylcellulose sodium and polymerized styrene
butadiene rubber (CMC+SBR), LA133, or LA132 or combinations
thereof. LA133 is an aqueous binder that is a water dispersion of
acrylonitrile multi-copolymer and LA132 is an aqueous binder, which
is believed to be a triblock copolymer of acrylamide, lithium
methacrylate, and acrylonitrile; both of these acrylonitrile
copolymers are available from Chengdu Indigo Power Sources Co.,
Ltd., Sichuan, P.R.C. Other suitable binders may include polyvinyl
alcohol (PVA), sodium alginate, or other water-soluble binders.
[0025] The negative electrode 16 may also include a conductive
filler present in an amount ranging from about 1 wt. % to about 15
wt. % based on the total weight of the negative electrode 16. The
conductive filler may be a conductive carbon material. The
conductive carbon material may be a high surface area carbon, such
as acetylene black (e.g., SUPER P.RTM. conductive carbon black from
Timcal Graphite & Carbon (Bodio, Switzerland)), graphite,
vapor-grown carbon fiber (VGCF), and/or carbon nanotubes.
Commercial forms of graphite that may be used are available from,
for example, Timcal Graphite & Carbon, Lonza Group (Basel,
Switzerland), or Superior Graphite (Chicago, Ill.). One specific
example is TIMREX.RTM. KS6 (primary synthetic graphite from Timcal
Graphite & Carbon. The vapor-grown carbon fiber may be in the
form of fibers having a diameter ranging from about 100 nm to about
200 nm, a length ranging from about 3 .mu.m to about 10 .mu.m, and
a BET surface area ranging from about 10 m.sup.2/g to about 20
m.sup.2/g. The carbon nanotubes may have a diameter ranging from
about 8 nm to about 25 nm and a length ranging from about 1 .mu.m
to about 20 .mu.m. Any one or more of the conductive fillers may be
included to ensure electron conduction between the active material
12 and a negative-side current collector 17 (copper or another
suitable material functioning as the negative terminal of the
battery 20).
[0026] The lithium ion battery 20 also includes the positive
electrode 18. The positive electrode 18 includes any lithium-based
active material that can sufficiently undergo lithium insertion and
deinsertion while aluminum or another suitable current collector 19
is functioning as the positive terminal of the lithium ion battery
20. One common class of known lithium-based active materials
suitable for the positive electrode 18 includes layered lithium
transition metal oxides. For example, the lithium-based active
material may be spinel lithium manganese oxide (LiMn.sub.2O.sub.4),
lithium cobalt oxide (LiCoO.sub.2), a manganese-nickel oxide spinel
[Li(Mn.sub.1.5Ni.sub.0.5)O.sub.2], a layered lithium nickel
manganese cobalt oxide (having a general formula of
xLi.sub.2MnO.sub.3.(1-x)LiMO.sub.2, where M is composed of any
ratio of Ni, Mn and/or Co). A specific example of the layered
lithium nickel manganese cobalt oxide includes
(xLi.sub.2MnO.sub.3.(1-x)Li(Ni.sub.1/3
Mn.sub.1/3Co.sub.1/3)O.sub.2). Other suitable lithium-based active
materials include Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2,
Li.sub.x+yMn.sub.2-yO.sub.4 (LMO, 0<x<1 and 0<y<0.1),
or a lithium iron polyanion oxide, such as lithium iron phosphate
(LiFePO.sub.4) or lithium iron fluorophosphate
(Li.sub.2FePO.sub.4F), or a lithium rich layer-structure. Still
other lithium based active materials may also be utilized, such as
LiNi.sub.1+xCo.sub.1-yM.sub.x+yO.sub.2 or
LiMn.sub.1.5-xNi.sub.0.5-yM.sub.x+yO.sub.4 (M is composed of any
ratio of Al, Ti, Cr, and/or Mg), stabilized lithium manganese oxide
spinel (Li.sub.xMn.sub.2-yM.sub.yO.sub.4, where M is composed of
any ratio of Al, Ti, Cr, and/or Mg), lithium nickel cobalt aluminum
oxide (e.g., LiNi.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2 or NCA),
aluminum stabilized lithium manganese oxide spinel (e.g.,
Li.sub.xAl.sub.0.05Mn.sub.0.95O.sub.2), lithium vanadium oxide
(LiV.sub.2O.sub.5), Li.sub.2MSiO.sub.4 (where M is composed of any
ratio of Co, Fe, and/or Mn), and any other high energy
nickel-manganese-cobalt material (HE-NMC, NMC or LiNiMnCoO.sub.2).
By "any ratio" it is meant that any element may be present in any
amount. So, in some examples, M could be Al, with or without Cr,
Ti, and/or Mg, or any other combination of the listed elements. In
another example, anion substitutions may be made in the lattice of
any example of the lithium transition metal based active material
to stabilize the crystal structure. For example, any O atom may be
substituted with an F atom. Still other examples of suitable active
materials for the positive electrode include V.sub.2O.sub.5 and
MnO.sub.2.
[0027] The positive electrode 18 may also include any of the
previously mentioned binder(s) and/or conductive filler(s). An
example of the composition of the positive electrode 18 includes
about 85 wt. % to about 95 wt. % of the active material, from about
1 wt. % to about 15 wt. % of the binder, and from about 1 wt. % to
about 15 wt. % of the conductive filler.
[0028] The lithium ion battery 20 also includes the porous polymer
separator 22 positioned between the positive and negative
electrodes 18, 16. The porous separator 22 operates as an
electrical insulator (preventing the occurrence of a short), a
mechanical support, and a barrier to prevent physical contact
between the two electrodes 18, 16. The porous separator 22 also
ensures passage of lithium ions (identified by the Li.sup.+)
through the non-aqueous electrolyte 10 filling its pores.
[0029] The porous polymer separator 22 may be formed, e.g., from a
polyolefin. The polyolefin may be a homopolymer (derived from a
single monomer constituent) or a heteropolymer (derived from more
than one monomer constituent), and may be either linear or
branched. If a heteropolymer derived from two monomer constituents
is employed, the polyolefin may assume any copolymer chain
arrangement including those of a block copolymer or a random
copolymer. The same holds true if the polyolefin is a heteropolymer
derived from more than two monomer constituents. As examples, the
polyolefin may be polyethylene (PE), polypropylene (PP), a blend of
PE and PP, or multi-layered structured porous films of PE and/or
PP. Commercially available porous separators 22 include single
layer polypropylene membranes, such as CELGARD 2400 and CELGARD
2500 from Celgard, LLC (Charlotte, N.C.). It is to be understood
that the porous separator 22 may be coated or treated, or uncoated
or untreated. For example, the porous separator 22 may or may not
be coated or include any surfactant treatment thereon.
[0030] In other examples, the porous separator 22 may be formed
from another polymer chosen from polyethylene terephthalate (PET),
polyvinylidene fluoride (PVdF), polyamides (Nylons), polyurethanes,
polycarbonates, polyesters, polyetheretherketones (PEEK),
polyethersulfones (PES), polyimides (PI), polyamide-imides,
polyethers, polyoxymethylene (e.g., acetal), polybutylene
terephthalate, polyethylenenaphthenate, polybutene, polyolefin
copolymers, acrylonitrile-butadiene styrene copolymers (ABS),
polystyrene copolymers, polymethylmethacrylate (PMMA), polyvinyl
chloride (PVC), polysiloxane polymers (such as polydimethylsiloxane
(PDMS)), polybenzimidazole (PBI), polybenzoxazole (PBO),
polyphenylenes (e.g., PARMAX.TM. (Mississippi Polymer Technologies,
Inc., Bay Saint Louis, Miss.)), polyarylene ether ketones,
polyperfluorocyclobutanes, polytetrafluoroethylene (PTFE),
polyvinylidene fluoride copolymers and terpolymers, polyvinylidene
chloride, polyvinylfluoride, liquid crystalline polymers (e.g.,
VECTRAN.TM. (Hoechst AG, Germany) and ZENITE.RTM. (DuPont,
Wilmington, Del.)), polyaramides, polyphenylene oxide, and/or
combinations thereof. It is believed that another example of a
liquid crystalline polymer that may be used for the porous
separator 22 is poly(p-hydroxybenzoic acid). In yet another
example, the porous separator 22 may be chosen from a combination
of the polyolefin (such as PE and/or PP) and one or more of the
other polymers listed above.
[0031] The porous separator 22 may be a single layer or may be a
multi-layer (e.g., bilayer, trilayer, etc.) laminate fabricated
from either a dry or wet process.
[0032] The non-aqueous electrolyte 10 of the lithium ion battery 20
may be any of the examples previously described, and includes the
solvent, the lithium salt, and the additive 14. Each of the
negative electrode 16, the porous polymer separator 22, and the
positive electrode 18 may be soaked in the non-aqueous electrolyte
10.
[0033] As shown in FIG. 2, the fully assembled lithium ion battery
20 may also include an external circuit 24 that connects the
current collectors 16, 18. The battery 20 may also support the load
device 26 that can be operatively connected to the external circuit
24. The load device 26 may receive a feed of electrical energy from
the electric current passing through the external circuit 24 when
the battery 20 is discharging. While the load device 26 may be any
number of known electrically-powered devices, a few specific
examples of a power-consuming load device include an electric motor
for a hybrid vehicle or an all-electrical vehicle, a laptop
computer, a cellular phone, and a cordless power tool. The load
device 26 may also, however, be a power-generating apparatus that
charges the battery 20 for purposes of storing energy. For
instance, the tendency of windmills and solar panels to variably
and/or intermittently generate electricity often results in a need
to store surplus energy for later use.
[0034] At the beginning of a discharge, the negative electrode 16
of the battery 20 contains a high concentration of inserted lithium
while the positive electrode 18 is relatively depleted. When the
negative electrode 16 contains a sufficiently higher relative
quantity of inserted lithium, the battery 20 can generate a
beneficial electric current by way of reversible electrochemical
reactions that occur when the external circuit 24 is closed to
connect the negative electrode 12 and the positive electrode 18.
The establishment of the closed external circuit under such
circumstances causes the extraction of inserted lithium from the
negative electrode 16. The extracted lithium atoms are split into
lithium ions (identified by the black dots and by the open circles
having a (+) charge) and electrons (e) as they leave the insertion
host (i.e., negative electrode 16).
[0035] The chemical potential difference between the electrodes 16,
18 drives the electrons (e.sup.-) produced by the oxidation of
inserted lithium at the negative electrode 16 through the external
circuit 24 towards the positive electrode 18. The lithium ions are
concurrently carried by the electrolyte through the porous polymer
separator 22 towards the positive electrode 18. The different
voltage potential windows disclosed herein may be used to control
the amount of lithium that is transported during cycling.
[0036] The electrons (e) flowing through the external circuit 24
and the lithium ions migrating across the porous polymer separator
22 in the electrolyte eventually reconcile and form inserted
lithium at the positive electrode 18. The electric current passing
through the external circuit 24 can be harnessed and directed
through the load device 26 until the level of lithium in the
negative electrode 16 falls below a workable level or the need for
electrical energy ceases.
[0037] The battery 20 may be recharged after a partial or full
discharge of its available capacity. To charge the battery 20, an
external battery charger is connected to the positive and the
negative electrodes 16, 18, to drive the reverse of battery
discharge electrochemical reactions. During recharging, the
electrons (e) flow back toward the negative electrode 16 through
the external circuit 24, and the lithium ions are carried by the
electrolyte 10 across the porous polymer separator 22 back toward
the negative electrode 16. The electrons (e) and the lithium ions
are reunited at the negative electrode 16, thus replenishing it
with inserted lithium for consumption during the next battery
discharge cycle.
[0038] The external battery charger that may be used to charge the
battery 20 may vary depending on the size, construction, and
particular end-use of the battery 20. Some suitable external
battery chargers include a battery charger plugged into an AC wall
outlet and a motor vehicle alternator.
[0039] To further illustrate the present disclosure, an example is
given herein. It is to be understood that this example is provided
for illustrative purposes and is not to be construed as limiting
the scope of the present disclosure.
EXAMPLE
[0040] Five single layer pouch cells were prepared, each with a
lithium titanate (LTO) negative electrode, a lithium manganese
oxide (LMO) positive electrode, PVDF as the binder, SP, KS6, and
VGCF as conductive fillers. Two comparative example pouch cells
(C1, C2) included an electrolyte of 1.0 M LiPF.sub.6 in a solvent
mixture including propylene carbonate, ethylene carbonate, dimethyl
carbonate, diethyl carbonate, and methyl butyrate (e.g.,
15:5:5:5:70 v/v). Three example pouch cells (E1, E2, and E3)
included the same electrolyte, and also included 2 wt. % of
triethyl chlorosilane as the additive. In each of the cells, the
separator was CELGARD.RTM. 2325.
[0041] The cells were tested under three different protocols.
[0042] The first protocol involved a formation step. In this step,
a constant current and constant voltage (CCCV) protocol was
applied. The cells were first charged at 0.05 C rate to 2.7 V, and
then the cell voltage was kept constant until the current dropped
to 0.01 C. Then, the cells were discharged at 0.1 C rate to the
cutoff voltage of 1.5 V. The cells went through 3 such formation
cycles before continuing into the second protocol.
[0043] The second protocol involved an aging step. In this step,
the cells were charged at 0.2 C rate until 100% State of Charge
(SOC), and then rested at 70.degree. C. for 7 days. Following the
aging process, the cells were degassed by cutting down the extra
gas bag. After 24 hours of open-circuit resting, the cells were
charged and discharged for 3 cycles at 1 C rate. In the cell
charge/discharge cycling test, a similar CCCV protocol was
followed. At 25.degree. C., the cells were first charged at 1 C
rate to 2.7 V, followed with constant voltage control until the
current dropped to 0.05 C. Then, the cells were subsequently
discharged at 1 C rate to the cutoff voltage of 1.5 V.
[0044] The third protocol involved a final aging step. In this
step, the cells were charged at 0.2 C rate until 100% State of
Charge (SOC), and then rested at 70.degree. C. for 7 days. After 24
hours of open-circuit resting at 25.degree. C., the cells were
charged and discharged for 3 cycles at 1 C rate. In the cell
charge/discharge cycling test, a similar CCCV protocol was
followed.
[0045] The capacity of the comparative and example cells was
measured for each of the cells during each of the tests. The
capacity of the comparative and example cells after the second
protocol test was performed are shown in Table 1. The DC resistance
(DCR) of the comparative and example cells was determined after the
second protocol test, and these results are also shown in Table 1.
Table 1 also illustrates the capacity remaining rate, average
capacity, and DCR of the comparative and example cells after the
third protocol test was performed, and the gas increase rate of the
example cells as compared with the comparative cells after the
third protocol test.
TABLE-US-00001 TABLE 1 Capacity DCR after Capacity Average Gas
after 2.sup.nd 2.sup.nd Protocol remaining rate Capacity after DCR
after increase Protocol Test Test after final aging final aging
final aging rate Cell (mAh) (.OMEGA.) (%) (mAh) (.OMEGA.) (%) C1
12.1 0.7517 0.0 11.5 1.1321 0 C2 12.8 0.7720 0.0 1.8901 E1 13.6
0.6328 24.3 11.1 1.1016 -47.6 E2 13.1 0.6490 20.2 1.0877 E3 12.9
0.8087 43.5 1.0242
[0046] As depicted from the results in Table 1, the additive in the
electrolyte of the example cells E1, E2, and E2 reduced the gassing
by 50% (as compared with cells C1 and C2, which were similar but
had no additive) and also improved the calendar life of the example
cells.
[0047] It is to be understood that the ranges provided herein
include the stated range and any value or sub-range within the
stated range. For example, a range from about 0.01 wt. % to about
10 wt. % should be interpreted to include not only the explicitly
recited limits of about 0.01 wt. % to about 10 wt. %, but also to
include individual values, such as 0.1 wt. %, 3.5 wt. %, 7 wt. %,
etc., and sub-ranges, such as from about 0.5 wt. % to about 9 wt.
%, etc. Furthermore, when "about" is utilized to describe a value,
this is meant to encompass minor variations (up to .+-.10%) from
the stated value.
[0048] Reference throughout the specification to "one example",
"another example", "an example", and so forth, means that a
particular element (e.g., feature, structure, and/or
characteristic) described in connection with the example is
included in at least one example described herein, and may or may
not be present in other examples. In addition, it is to be
understood that the described elements for any example may be
combined in any suitable manner in the various examples unless the
context clearly dictates otherwise.
[0049] In describing and claiming the examples disclosed herein,
the singular forms "a", "an", and "the" include plural referents
unless the context clearly dictates otherwise.
[0050] While several examples have been described in detail, it is
to be understood that the disclosed examples may be modified.
Therefore, the foregoing description is to be considered
non-limiting.
* * * * *